|
| |
|
|
A097648
|
|
a(n) is the least non-palindromic number m such that phi(m)=phi(reversal(m))=4*10^(n+2), or 0 if no such number exists.
|
|
1
| |
|
|
10040, 110440, 1014040, 11154440, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
COMMENTS
| This sequence is a subsequence of A097647. It seems that 10 divides all terms of this sequence. Conjecture: This sequence is infinite.
|
|
|
LINKS
| C. Rivera, f(p)=f(p') , puzzle 282
|
|
|
FORMULA
| a[n_]:=(For[m=4*10^(n+2), !(m!=FromDigits[Reverse[IntegerDigits[m]]] &&EulerPhi[m]==EulerPhi[FromDigits[Reverse[IntegerDigits [m]]]]==4*10^(n+2)), m++ ];m)
|
|
|
EXAMPLE
| a(4)=11154440 because phi(11154440)=phi(04445111)=4000000 and 11154440 is the earliest non-palindromic number with this property.
|
|
|
MATHEMATICA
| a[n_]:=(For[m=4*10^(n+2), !(m!=FromDigits[Reverse[IntegerDigits[m]]] &&EulerPhi[m]==EulerPhi[FromDigits[Reverse[IntegerDigits [m]]]]==4*10^(n+2)), m++ ]; m); Do[Print[a[n]], {n, 4}]
|
|
|
CROSSREFS
| Cf. A097647.
Sequence in context: A146505 A202653 A205822 * A188663 A203089 A023356
Adjacent sequences: A097645 A097646 A097647 * A097649 A097650 A097651
|
|
|
KEYWORD
| more,nonn,base
|
|
|
AUTHOR
| Farideh Firoozbakht (mymontain(AT)yahoo.com), Sep 04 2004
|
|
|
EXTENSIONS
| Better definition and more terms from David Wasserman (dwasserm(AT)earthlink.net), Dec 28 2007
a(27)=a(28)=...=a(32)=0 from Max Alekseyev (maxale(AT)gmail.com), Oct 17 2008
|
| |
|
|
